This application is related to co-pending application Ser. No. 07/988,246 filed Dec. 9, 1992, which is assigned to the assignee of the present application and which is incorporated herein by referent.
1. I. Field of the Invention
The present invention relates generally to management of the initial communication between a pair of nodes in a data transmission network prior to the insertion of a station into the data transmission ring. More particularly, a user interface is provided that permits the user to control the pseudo code signaling that occurs during the connection management sequence.
2. Discussion of the Prior Art
One type of high speed data transmission network is defined by the Fiber Distributed Data Interface (FDDI) protocol. The FDDI protocol is an American National Standards Institute (ANSI) data transmission standard which applies to a 100 Mbit/second token ring network that utilizes an optical fiber transmission medium. The FDDI protocol is intended as a high performance interconnection between a number of computers as well as between the computers and their associated mass storage subsystem(s) and other peripheral equipment.
Information is transmitted on an FDDI ring in frames that consist of 5-bit characters or "symbols", each symbol representing 4 data bits. Information is typically transmitted in symbol pairs or "bytes". Tokens are used to signify the right to transmit data between stations. The FDDI standard includes a thirty-two member symbol set. Within the set, sixteen symbols are data symbols (each representing 4 bits of ordinary data) and eight are control symbols. The eight control symbols are: J (the first symbol of a start delimiter byte JK), K (the second symbol of a start delimiter byte JK). I (Idle), H (Halt), Q (Quiet), T (End Delimiter), S (Set) and R (Reset). The remaining eight symbols of the FDDI standard symbols set are not used since they violate code run length and DC balance requirements of the protocol. These are referred to as V (violation) symbols.
In operation, a continuous stream of control symbol patterns defines a "line state". The FDDI protocol defines several line states, which include the following line states that are used during the connection management sequence:
(1) Idle Line State (ILS), which is a continuous stream of Idle symbols; PA1 (2) Quiet Line Sate (QLS),which is a continuous stream of Quiet symbols; PA1 (3) Halt Line State (HLS), which is a continuous stream of Halt symbols; PA1 (4) Master Line State (MLS), which is an alternating stream of Halt and Quiet symbols; and PA1 (5) Active Line State (ALS), which is the state used to transmit data units (frames)
The FDDI Station Management (SMT) standard provides the necessary control of an FDDI station (node) so that the node may work cooperatively as a part of an FDDI network. To effectively implement the functions required. SMT is divided into three entities, namely the Connection Management entity (CMT), the Ring Management entity (RMT) and the Frame Based Services. The Connection Management (CMT) is the management entity in the Station Management that is responsible for the station's port(s), as well as the connection to the ports of neighboring stations.
The Connection Management is further divided into three sub-entities. They include, the Physical Connection Management (PCM), Configuration Management (CFM) and Entity Coordination Management (ECM).
The introduction of an FDDI station (node) into the data flow path of the FDDI ring is governed by the Physical Connection Management (PCM) entity. To accomplish this, the PCM initializes the connection to neighboring ports and manages the line state signalling. Therefore, the PCM provides all of the necessary signalling to initialize a connection, to withhold a connection on a marginal line and to support maintenance. One of the most important functions of PCM is to establish a connection between two neighboring ports that are directly connected. In order to manage the initial connection between the ports of separate stations, the PCM manages the physical layer, controls the line-states transmitted during initiation and monitors the line-states received during the connection initialization. The PCM block itself is generically subdivided into two entities. The PCM state machine and the PCM pseudo code. The PCM state machine contains all the state and timing information of the PCM and provides a signalling channel. The PCM pseudo code specifies the pseudo code bits that are to be signalled by the PCM state machine and processes the bits received from the PCM at the other end of the link.
The connection process is achieved through a lock-step handshaking procedure. In the basic FDDI sequence, the handshaking procedure controlled by the PCM is divided into three stages. They include an initialization sequence, a signaling sequence and a join sequence. The initialization sequence is used to indicate the beginning of the PCM handshaking process. It forces the neighboring PCM into a known state so that the two PCM state machines can run in a lock-step fashion.
Following the initialization sequence is the signaling sequence. The signaling sequence communicates basic information about the port and he node with the neighboring port. A Link Confidence Test (LCT) is also conducted during the signaling sequence to test the link quality between the two ports. If the link quality is not acceptable or the type of connection is not supported or is currently not accepted by the nodes then the connection will be withheld. If the connection is not withheld during the signaling sequence, the PCM state machine can move on to the join sequence and establish a connection between the two neighboring ports.
A general description of the Station Management standard, as well as each of its subparts, including the PCM is described in detail in the draft ANSI FDDI Station Management Standard, dated Jun. 25, 1992, which is incorporated herein by reference.
The basic FDDI protocol has a defined connection management sequence for making a duplex connection between a pair of stations. As seen in FIG. 1, the PCM State Machine is likely to enter a total of seven states during the connection sequence. These include the following states: PC1:Break; PC3:Connect; PC4:Next; PC5:Signal; PC6:Join; PC7:Verify; and PC8:Active.
The PCM pseudo code machine is started in the Next state. The Next state is one of the two states used in the signaling sequence. The main purpose of the Next state is to separate the "bit" signaling performed in the Signal state (PC5). The Next state is also used to transmit Protocol Data Units (PDUs) while a loop test such as a Link Confidence Test or optionally, a Media Access Control Layer (MAC) Local Loop Test is performed.
On initial entry into the Next state, a continuous stream of Idle symbols is transmitted. While in the Next state, either a continuous stream of Idle symbols or a PDU symbol stream is transmitted. The Next state terminates and the state machine transits to the Signal state (PC5) upon the reception of either a Halt or a Master line state after a loop is performed. The same transition is made when a PC.sub.-- Signal signal is received from the Pseudo Code machine. When a PC.sub.-- Join signal is received, a transition is made to the Join state.
The Signal state is the second state used in the pseudo code signaling sequence. In the Signal state, individual bits of information are communicated between ports by transmitting either Halt symbols or Master symbols. The transmission of a Halt line state is equated with a logical one, and the transmission of the Master line state is a logical zero. Once each individual bit has been transmitted and received, the state machine returns to the Next state (i.e. the transmission of the Idle line state), before returning to the Signal state to transmit the next bit of information. Thus, the Next state is used as a bit delimiter between two signaling bits. When all signal bits have been transmitted and received, the Signaling sequence ends.
The pseudo code information that is transmitted as the state machine moves back and forth between the Next and Signal states is used by each station to provide information necessary to the connection process such as the port type and compatibility, the duration and results of the link confidence test and various information about the availability of the MAC for various purposes. The meaning of each bit is further explained in the proposed FDDI Station Management Standard referenced above.
The basic FDDI protocol (referred to as FDDI-1) has a defined connection management sequence as seen in FIG. 2a. The ANSI standards committee is currently working on an enhanced version of FDDI, which is generally referred to as the FDDI-II standard. At the time of this writing, the connection management sequence for FDDI-II had not been finalized. However, there are several proposed connection management sequences for FDDI-II. One such proposed sequence for a duplex connection is shown in FIG. 2b. As seen therein, it is expected that the sequence will be generally similar schematically to the protocol for a FDDI-I connection. Similarly, the state machine for a FDDI-II duplex connection is expected to be essentially the same as he state machine for a basic FDDI-1 connection. However, the information carried in the various pseudo code bits is expected to be somewhat different.
Since FDDI standards have not yet been finalized, and indeed are likely to be subject to change for some time, it is desirable for system designers to have a single chip set that can not only accommodate each of these different connection management sequences, but also remains adaptable to accommodate emerging FDDI standards and specialized user requirements.